My gut initial reaction of this one was that it is sweet. These last two iterations had me thinking they were awesome right out of the gate.
Reducing the Evoker's HP loss actually has me excited for the effect now. The transparency around Wizard balancing on your end, Jeff, is greatly appreciated; that adds to my liking of this effect/design. Losing the spellbook and familiar along the way is a bummer, but they are proper effects that deserve their own time in the spotlight. I think delaying their abilities is a good call -even as much as I liked them.
The sliding ability on the legendary is super cool -and triple damage too. WOW -that is gonna be awesome when that lands. I've always enjoyed the sliding spells, but I hope this will get others amped up to mix it up at the combat board.
The boost to the skill check is neat too. I do really like the idea of the big skill check still from last version; taking tests out of the game entirely doesn't feel quite right. If streamlining is the goal, this will achieve it though.
If auto success is only present for speed purposes, would a planar chart sticker on the combat board do the trick? The player will already by next to the board as to speak to the DM, plus it might "hide" the combat rooms better as the astral plane won't just be hanging in the corner. I'm still going to advocate for a method to indicate that planar charts are memorized and damage included that way; in which case the tests still had to be completed -just in advance.
I would like to say my thoughts haven't been swayed a bit after reading some comments, but they have. I can see how some people don't find these exciting. Its weird for the non-Bard Cabal members since there weren't really any casting based neck slot UR's (besides MoMM) to base an opinion on for a relic/legendary progression for each unique class. Some small things that might push people to love the designs and be excited:
1.One suggestion would be to just give and addition +3/+5 focus at the relic/legendary levels to "simulate passing" the checks and still have a smaller boosted skill check (+6)? This way those that don't want to don't have to, but those that do still have a leg up on those that do not test.
2.Can the relic give slide spells the ability to crit but only on a 20 and only for 2x? A small chance of success, but this leads to the progression of the legendary? Unless the sliding part of the legendary is supposed to be the fun effect, in which case forget this part.
3.Another idea would be to give the relic the option to cast a spell as a free action X/game and the legendary be Y/game. Or something of the sort. This would align with the "powering up" of the relic to legendary progression seen in other class necklaces (i.e. Fury with the Barbarian). Would also alleviate the pain many felt from the loss of the (at one point) 8 Free Action spells and still be good with the Cabal set.
4.Allowing the MEC to double all damage of a spell when evoked on a certain frequency.
Any of these would be cool, definitely not all.
Overall, I still think these are awesome and certainly can't wait to slide that 19 and make an arcane explosion. I still think it's an awesome time to be a Wizard.
. And maybe a few +5 Blessed Designs of Finality after that. 
